Surface modified particulate and sintered or injection molded products

ABSTRACT

Disclosed are interfacially modified particulate and polymer composite material for use in injection molding processes, such as metal injection molding and additive process such as 3D printing. The composite material is uniquely adapted for powder metallurgy processes. Improved products are provided under process conditions through surface modified powders that are produced by extrusion, injection molding, additive processes such as 3D printing, Press and Sinter, or rapid prototyping.

This application is a continuation application of the divisionalapplication Ser. No. 15/291,727, filed Oct. 12, 2016, which claimspriority to application Ser. No. 14/329,274, filed Jul. 11, 2014 (nowU.S. Pat. No. 9,512,544), which claims priority to U.S. provisionalapplication No. 61/845,007 filed on Jul. 11, 2013 and titled “SURFACEMODIFIED METAL PARTICULATE FOR POWDER METALLURGY AND PRODUCTS”. Theentire disclosures of all being incorporated herein by reference.

FIELD

Embodiments disclosed herein relate to interfacially modifiedparticulate and polymer composite material for use in part or componentmaking processes like injection molding processes, such as metalinjection molding and additive manufacturing, such as 3D printing. Thecomposite material is uniquely adapted for powder metallurgy processes.Improved products are provided under process conditions through surfacemodified powders that are produced by extrusion, injection molding, 3Dprinting, or rapid prototyping.

BACKGROUND

The use of inorganic or metal powders in injection molding, press andcenter and in metal injection molding (MIM) processes is a maturetechnology. Recent developments include the utility of new materials andmanufacturing techniques. For example, injection molding and 3D printinguses a variety of inorganic and metallic powders as a raw material fromwhich a variety of product shapes and parts can be made (e.g.) by metalinjection molding (MIM) and 3D printing. In particular, precise shapesthat perform uses in many commercial and consumer based products havebeen made. Applications include automotive applications, aerospaceapplications, consumer durable goods, computer applications, medicalapplications and others. Inorganic and/or metal powders are consolidatedor densified into specific shapes through a number of differentproduction processes.

In general, powder injection molded products are made by obtainingdesirable raw materials, such as inorganic, ceramic or elemental oralloy metal powders. These powders can be combined with optionaladditives, such as resins, waxes, graphite, dyes or lubricants which canbe mixed and then formed into an initial shape using hot or coldcompaction techniques. Typically, the initially formed shaped materialis sintered during the hot compaction stage or after the cold compactionstage to obtain a shaped inorganic or metal object in which the bondsbetween individual particles form as direct particle to particle bonds.After initial processing, finishing steps including machining, heattreatment, steam treatment, composite formation, plating, etc. can beused in forming a final finished product. Press and Sinter and MIMforming can reduce cost and produce a wide variety of simple and complexfinished products in low cost processing techniques.

A substantial need for the improvement of the forming or compaction stephas been noted in the industry. The feedstock of the powder material isoften difficult to process into the mold or through an orifice useful in3D printing due to the materials lack of viscoelastic, such as flowcharacteristics, physical and mechanical properties, and lack ofself-ordering and packing of particle fractions. In certain instances,the products made with MIM, Press and Sinter or 3D printing processes donot have the commercially effective physical properties for manyapplications. Often, the formed objects, green body and/or brown body,have defects such as an absence of strength, density, or other neededproperties as a result of insufficient particle packing and subsequentinefficient particle bonding. Further, the energy required to initiallyconform or eject the particulate mass to a particular shape such thatthe shape is complete and well-formed is excessive. The machines thatinitially form or compact the objects do not uniformly or fully fill,the whole space with powder resulting in a malformed part or unit.

Particle and polymer mixtures in which a finely divided powder orparticulate is dispersed have been suggested for MIM. Catamold®, a BASFproduct, is a material for metal and ceramic injection molding based onpolyacetal resin combined with stainless steels, special alloys orceramics. However, Catamold® particulate material is not surface coatedand does not have viscoelastic properties or particle packing propertiesin the resin that are helpful to injection molding and 3D printingprocesses. U.S. Pat. No. 7,153,594 B2, Kejzelman et. al., disclosesorganic coatings and lubricants for ferromagnetic chosen fromorgano-silane, organo-titanate, organo-aluminate or organo-zirconatecompounds without a polymer. Without the polymer phase, Kejzelman cannothave viscoelastic properties or particle packing properties.

A substantial need exists to improve powder injection techniques suchthat the products are improved, the energy to form the part is reducedand the part formed in the process is complete without themalformations.

BRIEF DESCRIPTION

We have found that by forming an inorganic, ceramic or metal particulatecomprising a particle with a coating of an interfacial modifier on theparticle and combined with a thermoplastic polymer can result in aninorganic polymer composite with high particle packing fractions andviscoelastic properties, such as melt flow, that can be readily formedinto a useful product via additive manufacturing and/or sintering.

The embodiment further relates to a particulate material with a coatingof an interfacial modifier and thermoplastic polymer that through theselection of particle type, particle size, particle shape, andinterfacial modifier can form a composite to provide substantiallyimproved extruded, injection molded, and 3D printed products. Thecoating of interfacial modifier on the particulate results in reducedshrinkage of the mass of particulate in the part or shaped articleduring the processes. Reduced shrinkage provides reproducibility of thepart or shaped article. Further, the interfacial modifier permits veryhigh packing fractions of the particles as the particles tend toself-order themselves to achieve the highest packing density in a volumeof the particles. The resulting molded products can exceed contemporaryproducts at least in tensile strength, impact strength and density.

We have found that by using an interfacially modified coated particulatethat the extrusion, injection molding, and 3D printing processes can beimproved by providing viscoelastic properties, such as increasing flowrates and reducing process pressures, during the extrusion, injectionmolding or 3D printing processes. Further, we have found that the greenbody and final products of the extrusion, 3D printing processes andinjection molding processes can be improved through the increasedpacking density of the particulate in the green and final products. Thepacking density, or packing fraction, is a useful predictor of theproperties of the resulting products. The improved packing densitytypically has improved strength, shielding properties, shape,definition, etc. of the final sintered product or shaped article formedby 3D printing.

In one embodiment, a selected particulate having specified particlemetallurgy can be combined with a specific amount of an interfacialmodifier to form a coating of the modifier on a particle and combinedwith a thermoplastic polymer to form a green body by injection moldingprior to sintering.

In another embodiment a selected particulate having specified particlemetallurgy can be combined with a specific amount of an interfacialmodifier to form a coating of the modifier on a particle and combinedwith a thermoplastic polymer to form a wire or feedstock useful for 3Dprinting.

In one embodiment, a selected particulate having specified particlemetallurgy can be combined with a specific amount of an interfacialmodifier to form a coating of the modifier on a particle and combinedwith a thermoplastic polymer to form a green body by press and sinteringtechniques prior to sintering.

In another embodiment, an extrusion process can be used with theinterfacially modified particulate to obtain improved processingproperties. Using the interfacial modifier, the extrusion producedproducts and injection molding products, including the green product,filaments, and the final sintered product, can be obtained with minimumexcluded volume and maximum particulate packing densities.

For the purpose of this disclosure, the term “green strength” or “greenproduct” indicates the nature of the property or product when initiallyformed in an injection molding processing prior to being heated orsintered to form the final shaped article.

The term “final shaped article” as used in this disclosure refers to thefinal product of the process, such that a final product is made by firstforming a green product and then sintering or heating the green productuntil it forms particle-to-particle bonding, necking, resulting in thefinal product shape.

For purposes of this disclosure, the term “feedstock” refers to materialthat is useful as material to form the roads or layers during 3Dprinting or deposition manufacture of an article. Feedstock material mayhave a circular, such as filaments or wire, or non-circularcross-sectional area, such as strips.

For the purpose of this disclosure, the term “filament” also called a“wire” refers to an elongated article having a cross-section and anindeterminate length. A cross-section can be round, elliptical, oval,triangular, rectangular, or can have an undefined or randomly shapedcross-section. The major dimension the cross-section can be at leastabout 0.1 millimeters it is often about 0.5 to either 1, 1.5, 2, 2.5, 3,3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7.0, 7.5, 8, 8.5, 9, 9.5 or 10 millimeters.The term “major dimension” refers to the largest dimension traversingthe cross-sectional area in the filament. The term “indeterminatelength” refers to a filament having a length substantially longer thanits major dimension. Such a filament can be produced and stored in reelsor other storage units upon which lengthy sections of filament areeasily maintained and later dispensed for use in 3-D filamentmanufacturing.

For the purpose of this disclosure, the term “particulate” refers to acollection of finely divided particles. The particulate has a range ofsizes and morphologies. The maximum particle size is less than 500microns. The particulate, coated with interfacial modifier, is dispersedinto a thermoplastic polymer. When used in a three-dimensionalmanufacturing technique, the filament or wire comprising the particulateis sintered at elevated temperature to form a desired object.

For the purpose of this disclosure, the term “elevated temperature”refers to a temperature sufficient or thermal process to cause thetemperature driven removal of polymeric materials, also called“debinding” from the filament or wire that is also sufficient to causethe particulate to form a solid object. Such object formation can occurby any temperature driven particulate bonding including softening,melting, particle to particle edge fusion.

For the purpose of this disclosure, the term “x-y plane” generallyrefers to a horizontally positioned claim orthogonal to the force ofgravity. The z-direction generally refers to the direction parallel tothe force of gravity and substantially orthogonal to the x-y plane.

For the purpose of this disclosure, the term “particulate” generallyrefers to a collection of particles with a defined particle size.

For the purpose of this disclosure, the term “object” or “part”generally refers to the product made using the filament or wire of thedisclosure after sintering. For the purpose of this disclosure, the term“pre-form object” generally refers to an object or part prior tosintering.

For the purpose of this disclosure, the term “mechanically shaped”generally refers to any modification in shape of a preform object duringfilament deposition or after filament deposition is complete.

For the purpose of this disclosure, the term “nonoxidizing atmosphere”generally refers to an atmosphere devoid of oxygen and can comprise asubstantial vacuum, nitrogen, hydrogen, a noble gas or mixtures thereof.The term “reducing atmosphere” also includes nonoxidizingcharacteristics but also includes the chemical nature that only theactions involving electrons can occur. A reducing atmosphere comprisesgases such as hydrogen, carbon monoxide, and other gaseous reactants.One aspect of a reducing atmosphere is that it can cause the removal ofoxygen from a metal or metal oxide.

The inorganic, ceramic or metallic particles typically have a particlesize that ranges from about 2 to 500, 2 to 400, 2 to 300, 2 to 200, or 2to 100 microns, 4 to 300, 4 to 200, or 4 to 100 microns, and often 5 to250, 5 to 150, 5 to 100, 5 to 75, or 5 to 50 microns. A combination of alarger and a smaller particle wherein there is about 0.1 to 25 wt. % ofthe smaller particle and about 99.9 to about 75 wt. % of largerparticles can be used where the ratio of the diameter of the largerparticles to the ratio of the smaller is about 2:1, 3:1, 4:1, 5:1, 6:1or 7:1. In some embodiments there may be three or more components ofparticle sizes such as 49:7:1 or 343:49:7:1. In other embodiments theremay be a continuous gradient of wide particle size distributions toprovide higher packing densities or packing fractions. These ratios willprovide optimum self-ordering of particles within the polymer phaseleading to tunable particle fractions within the composite material. Theself-ordering of the particles is improved with the addition ofinterfacial modifier as a coating on the surface of the particle.

The packing density or particle fraction of particles in the compositematerial varies to specifications required for the utility of the finalshaped product as formed via injection molding or 3D printing. Valuesfor packing density, volume percent, may be greater than 50, 55, 65, 7075, 80, 85, 90, 95, or 99%. Procedures to measure the loading ratio oftreated, or coated, particles in polymer is calculated based uponpyncnometer density and powder press density, as shown in Equation 1.

$\begin{matrix}{{{Maximum}\mspace{14mu}{Loading}} = \frac{{Powder}\mspace{14mu}{Puck}\mspace{14mu}{Density}}{{Pycnometer}\mspace{14mu}{Density}}} & \left( {{Eq}.\mspace{11mu} 1} \right)\end{matrix}$

We believe an interfacial modifier is a surface chemical treatment. Inone embodiment, the interfacial modifier is an organic material thatprovides an exterior coating on the particulate promoting the closeassociation of particulate to other particulate withoutintra-particulate bonding or attachment. Minimal amounts of theinterfacial modifier can be used including about 0.005 to 8 wt.-%, 0.005to 4 wt-%, 0.010 to 3 wt. %, 0.02 to 3 wt. % or about, 0.02 to 2 wt. %.The interfacial modifier coats but does not form any substantialcovalent bonding among or to other particulate or polymer.

DETAILED DISCUSSION

Interfacial modifiers provide the close association of the particulatewithin a particle distribution of one or many sizes. Interfacialmodifiers used in the application fall into broad categories including,for example, stearic acid derivatives, titanate compounds, zirconatecompounds, hafnium compounds, samarium compounds, strontium compounds,neodymium compounds, yttrium compounds, phosphonate compounds, aluminatecompounds. Useful, aluminate, phosphonate, titanate and zirconatecompounds useful contain from about 1 to about 3 ligands comprisinghydrocarbyl phosphate esters and/or hydrocarbyl sulfonate esters andabout 1 to 3 hydrocarbyl ligands which may further contain unsaturationand heteroatoms such as oxygen, nitrogen and sulfur. Commonly thetitanate and zirconate compounds contain from about 2 to about 3 ligandscomprising hydrocarbyl phosphate esters and/or hydrocarbyl sulfonateesters, commonly 3 of such ligands and about 1 to 2 hydrocarbyl ligands,commonly 1 hydrocarbyl ligand.

In one embodiment the interfacial modifier used is a type oforgano-metallic material such as organo-titanate, organo-boron,organo-aluminate, organo-strontium, organo-neodymium, organo-yttrium, ororgano-zirconate compounds. The specific type of organo-titanate,organo-aluminate, organo-hafnium, organo-strontium, organo-neodymium,organo-yttrium, or organo-zirconate compounds may be referred to asorgano-metallic compounds are distinguished by the presence of at leastone hydrolysable group and at least one organic moiety. Mixtures of theorgano-metallic materials may be used. The mixture of the interfacialmodifiers may be applied inter- or intra-particle, which means at leastone particle may has more than one interfacial modifier coating thesurface (intra), or more than one interfacial modifier coating may beapplied to different particles or particle size distributions (inter).These types of compounds may be defined by the following generalformula:M(R₁)_(n)(R₂)_(m)wherein M is a central atom selected from, for example, Ti, Al, Hf, Sa,Sr, Nd, Yt, and Zr; R₁ is a hydrolysable group; R₂ is a group consistingof an organic moiety; wherein the sum of m+n must equal the coordinationnumber of the central atom and where n is an integer ≥1 and m is aninteger ≥1.

Particularly R₁ is an alkoxy group having less than 12 carbon atoms.Useful are those alkoxy groups, which have less than 6, and most Usefulare alkoxy groups having 1-3 C atoms. R₂ is an organic group includingbetween 6-30, commonly 10-24 carbon atoms optionally including one ormore hetero atoms selected from the group consisting of N, O, S and P.R₂ is a group consisting of an organic moiety, which is not easilyhydrolysed and often lipophilic and can be a chain of an alkyl, ether,ester, phospho-alkyl, phospho-alkyl, phospho-lipid, or phospho-amine.The phosphorus may be present as phosphate, pyrophosphato, or phosphitogroups. Furthermore, R₂ may be linear, branched, cyclic, or aromatic.

Useful titanate and zirconate compounds include isopropyltri(dioctyl)pyrophosphato titanate (available from Kenrich Chemicalsunder the designation KR38S), neopentyl(diallyl)oxy,tri(dodecyl)benzene-sulfonyl titanate (available from Kenrich Chemicalsunder the trademark and designation LICA 09), neopentyl(diallyl)oxy,trioctylphosphato titanate (available from Kenrich Chemicals under thetrademark and designation LICA 12), neopentyl(diallyl)oxy,tri(dodecyl)benzene-sulfonyl zirconate (available from Kenrich Chemicalsunder the designation NZ 09), neopentyl(diallyl)oxy,tri(dioctyl)phosphato zirconate (available from Kenrich Chemicals underthe designation NZ 12), and neopentyl(diallyl)oxy,tri(dioctyl)pyro-phosphato zirconate (available from Kenrich Chemicalsunder the designation NZ 38). One embodiment is titanate istri(dodecyl)benzene-sulfonyl titanate (available from Kenrich Chemicalsunder the designation LICA 09). The interfacial modifiers modify theparticulate in the materials with the formation of a layer on thesurface of the particle reducing the intermolecular forces, improvingthe tendency of particle to mix with other particles, and resulting inincreased material density. Interfacial modifier coatings onparticulate, in contrast with uncoated particulate, maintain or improvethe viscoelastic properties of the base polymer in the compositematerial. For example, such viscoelastic properties may be melt flow,elasticity, tensile modulus, storage modulus, elastic-plasticdeformation and tensile elongation can be present in the compositematerial. Interfacial modifiers coatings on particulate also improve therheology of the composite material causing less wear on machinery andother technology useful in melt processing. Further, the interfacialmodifier coatings on particulate provide an inert surface on theparticulate substrate. The coated particulate is unreactive to the basepolymer or other additives in the composite material. In a sense, theinterfacial modifier coatings on particulate make the particulateinvisible or immiscible to the base polymer or other additives incontrast to particulate that is uncoated. Density is maximized as thenumber of close associations between the particulate surfaces.

The choice of interfacial modifiers is dictated by particulate, polymer,and application. The particle is completely and uniformly coated withthe interfacial modifier even if having substantial surface morphology.By substantial surface morphology, visual inspection would show a roughsurface to a particle substrate where the surface area of the roughsubstrate, taking into account the topography of the surface, issubstantially greater than the surface area of a smooth substrate.Amounts of the interfacial modifier can be used including about 0.005 to10 wt.-%, 0.005 to 5 wt-%, 0.005 to 4 wt-%, 0.010 to 3 wt. %, 0.02 to 3wt. % or about, 0.02 to 2 wt. %. Interfacial modifying coatings orsurface treatments may be applied to any particle type such as ceramic,inorganic, metal particulate or their mixtures. The maximum density of amaterial in the composite material with the polymer is a function of thedensities of the materials and the volume fractions of each. Higherdensity materials are achieved by maximizing per unit volume of thematerials with the highest densities and can be measured by applicationof Equation 1.

In the case of metals, the materials may be refractory metals such asniobium, molybdenum, tantalum, tungsten and rhenium and in someinstances titanium, vanadium, chromium, zirconium, hafnium, ruthenium,osmium and iridium. These materials are extremely hard, have a highmelting point, usually above 1500° C., and are difficult to deform.These materials may be formed into usable shapes using traditionalpowder metallurgy equipment. However, the maximum densities achievablewith conventional materials will be less then optimum and there may beexcessive shrinkage of the particulate mass upon sintering. When formingshaped articles, or linear extrudate, the inter-particle interactiondominates the behavior of the total material. Particles contact oneanother and the combination of irregular shape, interacting sharp edges,soft surfaces (resulting in gouging, points are usually work hardened)and the friction between the surfaces prevent further or optimalpacking. Therefore, maximizing properties, such as increasing the flowproperties, reducing viscosity, the particulate mass of a material, is afunction of softness of surface, hardness of edges, point size of point(sharpness), surface friction force and pressure on the material,circularity, and the usual, shape size distribution. In general, theseeffects are defined as particle surface energy interactions. Suchinteractions can be inhibitory to forming materials with requisiteproperties such as high density or low porosity. Further because of thisinter-particle friction, the forming pressure will decreaseexponentially with distance from the applied force.

Interfacially modifying chemistries are capable of modifying the surfaceof the particulate populations by a variety of means. For example, theremay be coordination bonding, Van der Waals forces, covalent bonding, ora combination of all three at the surface of the particulate with theinterfacial modifier. The interfacial modifier will be completely anduniformly associated with the surface of the particulate. In someinstances, the surface of the particulate will be completely coated bythe interfacial modifier. After treatment with the interfacial modifier,the surface of the particle behaves as a particle of the non-reacted endof the interfacial modifier. Thus the interfacial modifier associateswith the surface of the particle and in some cases the chemistry of theinterfacial modifier may form bonds with the surface of the particlethereby modifying the surface energy of the bulk particulate relative tothe surface characteristics of the interfacial modifier. However, theinterfacial modifier surface formed on a particle is non-reactive toother particles with a similar interfacially modified surface as well asto the polymer matrix. With interfacial modifiers the topography ofparticle surfaces, surface morphology, such as for example, roughness,irregular shape etc., is modified to reduce these inter-particle surfaceeffects. The particulate distribution with individual particles havingan interfacially modified surface, although perhaps comprising differentparticle sizes, has a more apparent homogeneous surface in comparison tonon-interfacially modified particulate. The interfacial modifierreduces, such as for example, surface energies on the particle surfacepermitting a denser packing of particle distributions. In one embodimentthe reduction of particle surface energy due to interfacial modificationof particle surfaces provides self-ordering of different particle sizesto proceed. In contrast, articles without interfacial modification willresist self-ordering. These organic materials of the interfacialmodifiers not only are non-reactive to each other but also reduce thefriction between particles thereby preventing gouging and allowing forgreater freedom of movement among and between particles in comparison toparticles that do not have a coating of interfacial modifier on theirsurface. These phenomena allow the applied shaping force to reach deeperinto the form resulting in a more uniform pressure gradient duringprocessing.

Metals

The powder particles can consist of a single crystal or many crystalgrains of various sizes. The micro structure including a crystal grainsize shape and orientation can also vary from metal to metal. Theparticle metallurgy depends on method of the particle fabrication.Metals that can be used in powder metal technology include copper metal,iron metal, nickel metal, tungsten metal, molybdenum, and metal alloysthereof and bi-metallic particles thereof. Often, such particles have anoxide layer that can interfere with shape formation. The metal particlecomposition used in particle metallurgy typically includes a largenumber of particulate size materials. The particles that are acceptablemolding grade particulate include particle size, particle sizedistribution, particle morphology, including reference index and aspectratio. Further, the flow rate of the particle mass, the green strengthof the initial shaped object, the compressibility of the initial shapedobject, the removability or ejectability of the shaped object from themold, and the dimensional stability of the initial shape duringprocessing and later sintering is also important.

Metal particulate that can be used in the composite materials for metalinjection molding or 3D printing include tungsten, uranium, osmium,iridium, platinum, rhenium, gold, neptunium, plutonium and tantalum.Other metals that can be used are iron, copper, nickel, cobalt, tin,bismuth and zinc. These metals may be used alone or in conjunction withother metals, inorganic minerals, ceramics, or glass bubbles andspheres. The end use of the material to make the shaped article would bethe determining factor. While an advantage is that non-toxic ornon-radioactive materials can be used as a substitute for lead anddepleted uranium where needed, lead and uranium can be used when thematerials have no adverse impact on the intended use. Another advantageis the ability to create bimetallic or higher materials that use two ormore metal materials that cannot naturally form an alloy. In anotherembodiment, using the Press and Sinter process, the coated particulatecan be formed into unique shapes for fuel pellets to enhance combustion.A variety of properties can be tailored through a careful selection ofmetal or a combination of metals and the toxicity or radioactivity ofthe materials can be designed into the materials as desired. Thesematerials are not used as large metal particles, but are typically usedas small metal particles, commonly called metal particulates. Suchparticulates have a relatively low aspect ratio and are typically lessthan about 1:3 aspect ratio. An aspect ratio is typically defined as theratio of the greatest dimension of the particulate divided by thesmallest dimension of the particulate. Generally, spherical particulatesare commonly used; however, sufficient packing densities can be obtainedfrom relatively uniformly shaped particles in a dense structure. In someembodiments, the particles may be ball milled to provide mostly roundparticles. In some instances the ball-milled particle can have some flatspots. In Press and Sinter processes, heterogeneous shapes and sizes aremore useful then spherical particulate. Using the interfacial modifiercoating enables the part or shaped article to be ejected from the diewith less force than a part or article that is not coated with theinterfacial modifier.

Ceramics

Another important inorganic material that can be used as a particulateincludes ceramic materials. Ceramics are typically classified into threedistinct material categories, including aluminum oxide and zirconiumoxide ceramic, metal carbide, metal boride, metal nitride, metalsilicide compounds, and ceramic material formed from clay or clay-typesources. Examples of useful technical ceramic materials are selectedfrom barium titanate, boron nitride, lead zirconate or lead tantalite,silicate aluminum oxynitride, silica carbide, silica nitride, magnesiumsilicate, titanium carbide, zinc oxide, and/or zinc dioxide (zirconia)particularly useful ceramics of use comprise the crystalline ceramics.Other embodiments include the silica aluminum ceramic materials that canbe made into useful particulate. Such ceramics are substantially waterinsoluble and have a particle size that ranges from about 10 to 500microns, have a density that ranges from about 1.5 to 3 gram/cc and arecommercially available. In an embodiment, soda lime glass may be useful.One useful ceramic product is the 3M ceramic microsphere material suchas the g-200, g-400, g-600, g-800 and g-850 products.

Magnetic composites can be made of any magnetic particle material thatwhen formed into a composite can be magnetized to obtain a permanentmagnetic field. These particles are typically inorganic and can beceramic. Magnetite is a mineral, one of the two common naturallyoccurring oxides of Iron (chemical formula Fe₃O₄) and a member of thespinel group. Magnetite is the most magnetic of all the naturallyoccurring minerals. Alnico magnet alloy is largely comprised ofaluminum, iron, cobalt and nickel. Alnico is a moderately expensivemagnet material because of the cobalt and nickel content. Alnico magnetalloy has a high maximum operating temperature and a very good corrosionresistance. Some grades of Alnico alloy can operate upwards of 5500° C.Samarium cobalt (SmCo) and Neodymium Iron Boron (NdFeB) are called rareearth because neodymium and samarium are found in the rare earthelements on the periodic table. Both samarium, cobalt, and neodymiummagnet alloys are powdered metals which are compacted in the presence ofa strong magnetic field and are then sintered. Ceramic magnet material(Ferrite) is strontium ferrite. Ceramic magnet material (Ferrite) is oneof the most cost effective magnetic materials manufactured in industry.The low cost is due to the cheap, abundant, and non-strategic rawmaterials used in manufacturing this alloy. The permanent ceramicmagnets made with this material lend themselves to large productionruns. Ceramic magnet material (Ferrite) has a fair to good resistance tocorrosion and it can operate in moderate heat.

Useful magnetic particles are ferrite materials. Ferrite is a chemicalcompound consisting of a ceramic inorganic oxide material. Ferric oxidecommonly represented as Fe₂O₃ is a principal component. Useful ferritematerials of the disclosure have at least some magnetic character andcan be used as permanent magnet ferrite cores for transformers and asmemory components in tape and disc and in other applications. Ferritematerials are ferromagnetic ceramic compounds generally derived fromiron oxides. Iron oxide compounds are materials containing iron andoxygen atoms. Most iron oxides do not exactly conform to a specificmolecular formula and can be represented as Fe₂O₃ or Fe₃O₄ as well ascompounds as Fe_(x)O_(y) wherein X is about 1 to 3 and Y is about 1 to4. The variation in these numbers result from the fundamental nature ofthe ferric oxide material which invoke often does not have preciselydefined ratios of iron to oxygen atoms. These materials are spinelferrites and are often in the form of a cubic crystalline structure. Thecrystalline usually synthetic ceramic material typically is manufacturedby manufacturing a ferric oxide material and at least one other metallicoxide material generally made from a metal oxide wherein the model is adivalent metal. Such metals include for example magnesium, calcium,barium, chrome manganese, nickel, copper, zinc, molybdenum and others.The Useful metals are magnesium, calcium and barium.

Useful ferrites are typically prepared using ceramic techniques. Oftenthe oxides are carbonates of the iron or divalent oxides are milleduntil a fine particulate is obtained. The fine particulate is dried andpre-fired in order to obtain the homogenous end product. The ferrite isthen often heated to form the final spinel crystalline structure. Thepreparation of ferrites is detailed in U.S. Pat. Nos. 2,723,238 and2,723,239. Ferrites are often used as magnetic cores in conductors andtransformers. Microwave devices such as glycerin tubes can use magneticmaterials. Ferrites can be used as information storage in the form oftape and disc and can be used in electromagnetic transistors and insimple magnet objects. One useful magnetic materials is known as zincferrite and has the formula ZnOFe₂₃. Another useful ferrite is thebarium ferrite that can be represented as BaO:6Fe₂ or BaFe₁₂O₁₉. Otherferrites includes soft ferrites such as manganese-zinc ferrite(Mn_(a)Zn_((1-a))Fe₂O₄) and nickel zinc ferrite Ni_(a)Zn_((1-a))Fe₂O₄.Other useful ferrites are hard ferrites including strontium ferriteSrFe₂O₄, cobalt ferrite CoFe₂O₄.

In some greater detail, ferrites are typically produced by heating amixture of finely divided metal oxide, carbonate or hydroxide withferrite powder precursors when pressed into a mold. During the heatingprocess the material is calcined. In calcination volatile materials areoften driven off leaving the inorganic oxides in the appropriate crystalstructure. Divalent metal oxide material is produced from carbonatesources. During calcination a mixture of oxide materials is producedfrom a heating or sintering of the blend, carbon dioxide is driven offleaving the divalent metal oxide. Such considering our high heatingprocesses similar to the firing of ceramic materials generally.

We have further found that a blend of the magnetic particle and one,two, three or more particles in particulate form can obtain importantcomposite properties from all of particulate materials in a polymercomposite structure. For example, a tungsten composite or other highdensity metal particulate can be blended with a second metal particulatethat provides to the relatively stable, non-toxic tungsten material,additional properties including a low degree of radiation in the form ofalpha, beta or gamma particles, a low degree of desired cytotoxicity, achange in appearance or other beneficial properties. One advantage of abimetallic composite is obtained by careful selection of proportionsresulting in a tailored magnetic strength for a particular end use. Suchcomposites each can have unique or special properties. These compositeprocesses and materials have the unique capacity and property that thecomposite acts as an alloy a blended composite of two or three differentmetals inorganic minerals that could not, due to melting point and otherprocessing difficulties, be made into an alloy form without thedisclosed embodiments.

Minerals

Examples of minerals that are useful in the embodiment include compoundssuch as Carbide, Nitride, Silicide and Phosphide; Sulphide, Selenide,Telluride, Arsenide and Bismuthide; Oxysulphide; Sulphosalt, such asSulpharsenite, Sulphobismuthite, Sulphostannate, Sulphogermanate,Sulpharsenate, Sulphantimonate, Sulphovanadate and Sulphohalide; Oxideand Hydroxide; Halides, such as Fluoride, Chloride, Bromide and Iodide;Fluoroborate and Fluorosilicate; Borate; Carbonate; Nitrate; Silicate;Silicate of Aluminum; Silicate Containing Aluminum or other Metals;Silicates containing other Anions; Niobate and Tantalate; Phosphate;Arsenate such as arsenate with phosphate (without other anions);Vanadate (vanadate with arsenate or phosphate); Phosphates, Arsenates orVanadate; Arsenite; Antimonate and Antimonite; Sulphate; Sulphate withHalide; Sulphite, Chromate, Molybdate and Tungstate; Selenite, Selenate,Tellurite, and Tellurate; Iodate; Thiocyanate; Oxalate, Citrate,Mellitate and Acetates include the arsenide, antimonide and bismuthideof e.g., metals such as Li, Na, Ca, Ba, Mg, Mn, Al, Ni, Zn, Ti, Fe, Cu,Ag and Au.

Garnet, is an important mineral and is a nesosilicate that complies withgeneral formula X₃Y₂(SiO₄)₃. The X is divalent cation, typically Ca²⁺,Mg²⁺, Fe²⁺ etc. and the Y is trivalent cation, typically Al³⁺, Fe³⁺,Cr³⁺, etc. in an octahedral/tetrahedral framework with [SiO₄]⁴⁻occupying the tetrahedral structure. Garnets are most often found in thedodecahedral form, less often in trapezo-hedral form.

One particularly useful inorganic material used are metal oxidematerials including aluminum oxide or zirconium oxide. Aluminum oxidecan be in an amorphous or crystalline form. Aluminum oxide is typicallyformed from sodium hydroxide, and aluminum ore. Aluminum oxide has adensity that is about 3.8 to 4 g-cc and can be obtained in a variety ofparticle sizes that fall generally in the range of about 10 to 1,000microns. Zirconium oxide is also a useful ceramic or inorganic material.Zirconium dioxide is crystalline and contains other oxide phases such asmagnesium oxide, calcium oxide or cerium oxide. Zirconium oxide has adensity of about 5.8 to 6 gm-cm⁻³ and is available in a variety ofparticle sizes. Another useful inorganic material concludes zirconiumsilicate. Zirconium silicate (ZrSiO₄) is an inorganic material of lowtoxicity that can be used as refractory materials. Zirconium dioxide hasa density that ranges from about 4 to 5 gm/cc and is also available in avariety of particulate forms and sizes.

One important inorganic material that can be used as a particulate inanother embodiment includes silica, silicon dioxide (SiO₂). Silica iscommonly found as sand or as quartz crystalline materials. Also, silicais the major component of the cell walls of diatoms commonly obtained asdiatomaceous earth. Silica, in the form of fused silica or glass, hasfused silica or silica line-glass as fumed silica, as diatomaceous earthor other forms of silica as a material density of about 2.7 gm-cm⁻³ buta particulate density that ranges from about 1.5 to 2 gm-cm⁻³.

Glass Spheres

Glass spheres (including both hollow and solid) are another usefulnon-metal or inorganic particulate. These spheres are strong enough toavoid being crushed or broken during further processing, such as by highpressure spraying, kneading, extrusion or injection molding. In manycases these spheres have particle sizes close to the sizes of otherparticulate if mixed together as one material. Thus, they distributeevenly, homogeneously, within the composite upon introduction andmixing. The method of expanding solid glass particles into hollow glassspheres by heating is well known. See, e.g., U.S. Pat. No. 3,365,315herein incorporated by reference in its entirety.

Useful hollow glass spheres having average densities of about 0.1grams-cm⁻³ to approximately 0.7 grams-cm⁻³ or about 0.125 grams-cm⁻³ toapproximately 0.6 grams-cm⁻³ are prepared by heating solid glassparticles.

For a product of hollow glass spheres having a particular desiredaverage density, there is an optimum sphere range of sizes of particlesmaking up that product which produces the maximum average strength. Acombination of a larger and a smaller glass sphere wherein there isabout 0.1 to 25 wt. % of the smaller sphere and about 99.9 to about 75wt. % of larger particles can be used were the ratio of the diameter ofthe larger particles to the ratio of the smaller is about 2:1, 3:1, 4:1,5:1, 6:1 or 7:1.

Glass spheres used within the embodiments can include both solid andhollow glass spheres. All the particles heated in the furnace do notexpand, and most hollow glass-sphere products are sold withoutseparating the hollow from the solid spheres.

Useful glass spheres are hollow spheres with relatively thin walls. Suchspheres typically comprise a silica-line-oral silicate glass and in bulkform a white powdery particulate. The density of the hollow sphericalmaterials tends to range from about 0.1 to 0.8 g/cc that issubstantially water insoluble and has an average particle diameter thatranges from about 10 to 250 microns.

Polymers

A large variety of polymer materials can be used with the interfaciallymodified particulate of the embodiment. For the purpose of thisapplication, a polymer is a general term covering either a thermoset ora thermoplastic polymer. We have found that polymer materials that areuseful include both condensation polymeric materials and addition orvinyl polymeric materials. Crystalline or semi-crystalline polymers,copolymers, blends and mixtures are useful. Included are both vinyl andcondensation polymers, and polymeric alloys thereof. Vinyl polymers aretypically manufactured by the polymerization of monomers having anethylenically unsaturated olefinic group. Condensation polymers aretypically prepared by a condensation polymerization reaction which istypically considered to be a stepwise chemical reaction in which two ormore molecules combined, often but not necessarily accompanied by theseparation of water or some other simple, typically volatile substance.Such polymers can be formed in a process called polycondensation. Thepolymer has a density of at least 0.85 gm-cm⁻³, however, polymers havinga density of greater than 0.96 are useful to enhance overall productdensity. A density is often up to 1.7 or up to 2 gm-cm⁻³ or can be about1.5 to 1.95 gm-cm⁻³ depending on metal particulate and end use.

Vinyl polymers include polyethylene, polypropylene, polybutylene,polyvinyl alcohol (PVA), acrylonitrile-butadiene-styrene (ABS),poly(methyl-pentene), (TPX®), polybutylene copolymers, polyacetylresins, polyacrylic resins, homopolymers or copolymers comprising vinylchloride, vinylidene chloride, fluorocarbon copolymers, etc.Condensation polymers include nylon, phenoxy resins, polyarylether suchas polyphenylether, polyphenylsulfide materials; polycarbonatematerials, chlorinated polyether resins, polyethersulfone resins,polyphenylene oxide resins, polysulfone resins, polyimide resins,thermoplastic urethane elastomers and many other resin materials.

Condensation polymers that are useful include polyamides,polyamide-imide polymers, polyarylsulfones, polycarbonate, polybutyleneterephthalate, polybutylene naphthalate, polyetherimides (such as, forexample, ULTEM®), polyethersulfones, polyethylene terephthalate,thermoplastic polyimides, polyphenylene ether blends, polyphenylenesulfide, polysulfones, thermoplastic polyurethanes and others. Usefulcondensation engineering polymers include polycarbonate materials,polyphenyleneoxide materials, and polyester materials includingpolyethylene terephthalate, polybutylene terephthalate, polyethylenenaphthalate and polybutylene naphthalate materials. Useful polycarbonatematerials should have a melt index between 0.5 and 7 gms/10 min,commonly between 1 and 5 gms/10 min.

A variety of polyester condensation polymer materials includingpolyethylene terephthalate, polybutylene terephthalate, polyethylenenaphthalate, polylactic acid, polybutylene naphthalate, etc. can beuseful in the composites. Such materials have a Useful molecular weightcharacterized by melt flow properties. Useful polyester materials have aviscosity at 265° C. of about 500-2000 cP, commonly about 800-1300 cP.

Polyphenylene oxide materials are engineering thermoplastics that areuseful at temperature ranges as high as 330° C. Polyphenylene oxide hasexcellent mechanical properties, dimensional stability, and dielectriccharacteristics. A Useful melt index (ASTM 1238) for the polyphenyleneoxide material useful typically ranges from about 1 to 20, commonlyabout 5 to 10 gm/10 min. The melt viscosity is about 1000 cP at 265° C.

Another class of thermoplastic includes styrenic copolymers. The termstyrenic copolymer indicates that styrene is copolymerized with a secondvinyl monomer resulting in a vinyl polymer. Such materials contain atleast a 5 mol-% styrene and the balance being 1 or more other vinylmonomers. An important class of these materials is styrene acrylonitrile(SAN) polymers. SAN polymers are random amorphous linear copolymersproduced by copolymerizing styrene acrylonitrile and optionally othermonomers. Emulsion, suspension and continuous mass polymerizationtechniques have been used. SAN copolymers possess transparency,excellent thermal properties, good chemical resistance and hardness.These polymers are also characterized by their rigidity, dimensionalstability and load bearing capability. Olefin modified SAN's (OSApolymer materials) and acrylic styrene acrylonitriles (ASA polymermaterials) are known. These materials are somewhat softer thanunmodified SAN's and are ductile, opaque, two phased terpolymers thathave surprisingly improved weatherability.

ASA polymers are random amorphous terpolymers produced either by masscopolymerization or by graft copolymerization. These materials can alsobe blended or alloyed with a variety of other polymers includingpolyvinyl chloride, polycarbonate, polymethyl methacrylate and others.An important class of styrene copolymers includes theacrylonitrile-butadiene-styrene monomers (ABS). These polymers are veryversatile family of engineering thermoplastics produced bycopolymerizing the three monomers. The styrene copolymer family ofpolymers has a melt index that ranges from about 0.5 to 25, commonlyabout 0.5 to 20.

Important classes of engineering polymers that are useful includeacrylic polymers. Acrylics comprise a broad array of polymers andcopolymers in which the major monomeric constituents are an esteracrylate or methacrylate. These polymers are often provided in the formof hard, clear sheet or pellets. A Useful acrylic polymer material thatis useful in an embodiment has a melt index of about 0.5 to 50, commonlyabout 1 to 30 gm/10 min.

Vinyl polymer polymers include acrylonitrile; polymer of alpha-olefinssuch as ethylene, high density polyethylene (HDPE), propylene, etc.;chlorinated monomers such as vinyl chloride, vinylidene dichloride,acrylate monomers such as acrylic acid, methylacrylate, methylmethacrylate, acrylamide, hydroxyethyl acrylate, and others; styrenicmonomers such as styrene, alpha methyl styrene, vinyl toluene, etc.;vinyl acetate; and other commonly available ethylenically unsaturatedmonomer compositions.

Polymer blends or polymer alloys can be useful in manufacturing thepellet or linear extrudate of the embodiments. Such alloys typicallycomprise two miscible polymers blended to form a uniform composition.Scientific and commercial progress in the area of polymer blends has ledto the realization that important physical property improvements can bemade not by developing new polymer material but by forming misciblepolymer blends or alloys. A polymer alloy at equilibrium comprises amixture of two amorphous polymers existing as a single phase ofintimately mixed segments of the two macro molecular components.Miscible amorphous polymers form glasses upon sufficient cooling and ahomogeneous or miscible polymer blend exhibits a single, compositiondependent glass transition temperature (Tg). Immiscible or non-alloyedblend of polymers typically displays two or more glass transitiontemperatures associated with immiscible polymer phases. In the simplestcases, the properties of polymer alloys reflect a composition weightedaverage of properties possessed by the components. In general, however,the property dependence on composition varies in a complex way with aparticular property, the nature of the components (glassy, rubbery orsemi-crystalline), the thermodynamic state of the blend, and itsmechanical state whether molecules and phases are oriented.

The primary requirement for the substantially thermoplastic engineeringpolymer material is that it retains sufficient thermoplastic properties,such as viscosity and stability, to permit melt processing, such as meltblending, with a metal particulate, permit formation of linear extrudatepellets, and to permit the composition material or pellet to be extrudedor injection molded in a thermoplastic process forming the usefulproduct or green product. Engineering polymer and polymer alloys areavailable from a number of manufacturers including Dyneon LLC, B.F.Goodrich, G.E., Dow, PolyOne, Mitsui, and DuPont.

Typically, polyesters are manufactured with a styrene concentration orother monomer concentration producing polymer having an uncuredviscosity of 200-1,000 mPa·s (cP). Specialty polymers may have aviscosity that ranges from about 20 cP to 2,000 cP.

Phenolic polymers can also be used in the manufacture of the structuralmembers. Phenolic polymers typically comprise a phenol-formaldehydepolymer. Such polymers are inherently fire resistant, heat resistant andare low in cost. Phenolic polymers are typically formulated by blendingphenol and less than a stoichiometric amount of formaldehyde. Thesematerials are condensed with an acid catalyst resulting in athermoplastic intermediate polymer called NOVOLAK.

Useful fluoropolymers are perflourinated and partially fluorinatedpolymers made with monomers containing one or more atoms of fluorine, orcopolymers of two or more of such monomers. Common examples offluorinated monomers useful in these polymers or copolymers includetetrafluoroethylene (TFE), hexafluoropropylene (HFP), vinylidenefluoride (VDF), perfluoroalkylvinyl ethers such asperfluoro-(n-propyl-vinyl) ether (PPVE) or perfluoromethylvinylether(PMVE). Other copolymerizable olefinic monomers, includingnon-fluorinated monomers, may also be present.

Thermoplastics include polyvinylchloride, polyphenylene sulfite, acrylichomopolymers, maleic anhydride containing polymers, acrylic materials,vinyl acetate polymers, diene containing copolymers such as1,3-butadiene, 1,4-pentadiene, halogen or chlorosulfonyl modifiedpolymers or other polymers. Condensation polymeric thermoplastics can beused including polyamides, polyesters, polycarbonates, polysulfones andsimilar polymer materials by reacting end groups with silanes havingamino-alkyl, chloroalkyl, isocyanato or similar functional groups.

Particularly useful materials for the fluoropolymers are TFE-HFP-VDFterpolymers (melting temperature of about 100 to 260° C.; melt flowindex at 265° C. under a 5 kg load is about 1-30 g-10 min⁻¹.),hexafluoropropylene-tetrafluoroethylene-ethylene (HTE) terpolymers(melting temperature about 150 to 280° C.; melt flow index at 297° C.under a 5 kg load of about 1-30 g-10 min⁻¹.),ethylene-tetrafluoroethylene (ETFE) copolymers (melting temperatureabout 250 to 275° C.; melt flow index at 297° C. under a 5 kg load ofabout 1-30 g-10 min⁻¹.), hexafluoropropylene-tetrafluoroethylene (FEP)copolymers (melting temperature about 250 to 275° C.; melt flow index at372° C. under a 5 kg load of about 1-30 g-10 min⁻¹.), andtetrafluoroethylene-perfluoro(alkoxy alkane) (PFA) copolymers (meltingtemperature about 300 to 320° C.; melt flow index at 372° C. under a 5kg load of about 1-30 g-10 min⁻¹.). Each of these fluoropolymers iscommercially available from Dyneon LLC, Oakdale, Minn. The TFE-HFP-VDFterpolymers are sold under the designation “THV”.

Also useful are vinylidene fluoride polymers primarily made up ofmonomers of vinylidene fluoride, including both homo polymers andcopolymers. Such copolymers include those containing at least 50 molepercent of vinylidene fluoride copolymerized with at least one comonomerselected from the group consisting of tetrafluoroethylene,trifluoroethylene, chlorotrifluoroethylene, hexafluoropropene, vinylfluoride, pentafluoropropene, and any other monomer that readilycopolymerizes with vinylidene fluoride. These materials are furtherdescribed in U.S. Pat. No. 4,569,978 (Barber) incorporated herein byreference. Useful copolymers are those composed of from at least about70 and up to 99 mole percent vinylidene fluoride, and correspondinglyfrom about 1 to 30 percent tetrafluoroethylene, such as disclosed inBritish Patent No. 827,308; and about 70 to 99 percent vinylidenefluoride and 1 to 30 percent hexafluoropropene (see for example U.S.Pat. No. 3,178,399); and about 70 to 99 mole percent vinylidene fluorideand 1 to 30 percent trifluoroethylene Terpolymers of vinylidenefluoride, trifluoroethylene and tetrafluoroethylene such as described inU.S. Pat. No. 2,968,649 and terpolymers of vinylidene fluoride,trifluoroethylene and tetrafluoroethylene are also representative of theclass of vinylidene fluoride copolymers which are useful. Such materialsare commercially available under the KYNAR trademark from Arkema Grouplocated in King of Prussia, Pa. or under the DYNEON trademark fromDyneon LLC of Oakdale, Minn. Fluorocarbon elastomer materials can alsobe used in the composite materials. Fluoropolymer contain VF₂ and HFPmonomers and optionally TFE and have a density greater than 1.8 gm-cm⁻³fluoropolymers exhibit good resistance to most oils, chemicals,solvents, and halogenated hydrocarbons, and an excellent resistance toozone, oxygen, and weathering. Their useful application temperaturerange is −40° C. to 300° C. Fluoroelastomer examples include thosedescribed in detail in Lentz, U.S. Pat. No. 4,257,699, as well as thosedescribed in Eddy et al., U.S. Pat. No. 5,017,432 and Ferguson et al.,U.S. Pat. No. 5,061,965. The disclosures of each of these patents aretotally incorporated herein by reference.

Latex fluoropolymers are available in the form of the polymerscomprising the PFA, FEP, ETFE, HTE, THV and PVDF monomers. Fluorinatedpoly(meth)acrylates can generally be prepared by free radicalpolymerization either neat or in solvent, using radical initiators wellknown to those skilled in the art. Other monomers which can becopolymerized with these fluorinated (meth)acrylate monomers includealkyl (meth)acrylates, substituted alkyl (meth)acrylates, (meth)acrylicacid, (meth)acrylamides, styrenes, vinyl halides, and vinyl esters. Thefluoropolymers can comprise polar constituents. Such polar groups orpolar group containing monomers may be anionic, nonionic, cationic, oramphoteric. In general, the more commonly employed polar groups or polargroup-containing organic radicals include organic acids, particularlycarboxylic acid, sulfonic acid and phosphonic acid; carboxylate salts,sulfonates, phosphonates, phosphate esters, ammonium salts, amines,amides, alkyl amides, alkyl aryl amides, imides, sulfonamides,hydroxymethyl thiols, esters, silanes, and polyoxyalkylenes, as well asother organic radicals such as alkylene or arylene substituted with oneor more of such polar groups. The latex fluoropolymers described hereinare typically aqueous dispersed solids but solvent materials can beused. The fluoropolymer can combined with various solvents to formemulsion, solution or dispersion in a liquid form. Dispersions offluoropolymers can be prepared using conventional emulsionpolymerization techniques, such as described in U.S. Pat. Nos.4,418,186; 5,214,106; 5,639,838; 5,696,216 or Modern Fluoropolymers,Edited by John Scheirs, 1997 (particularly pp. 71-101 and 597-614). Theliquid forms can be further diluted in order to deliver the desiredconcentration. Although aqueous emulsions, solutions, and dispersionsare Useful, up to about 50% of a cosolvent such as methanol,isopropanol, or methyl perfluorobutyl ether may be added. Commonly, theaqueous emulsions, solutions, and dispersions comprise less than about30% cosolvent, more commonly less than about 10% cosolvent, and mostcommonly the aqueous emulsions, solutions, and dispersions aresubstantially free of cosolvent.

The choice of the polymer for the composite to make the green body forMIM or the feedstock for 3D printing may depend on a wide number ofindependent and interdependent variables. Understanding of thesevariables and their interactions may require some preliminary testingsuch as, for example, melt flow rates, viscosity, and density of thecomposite material so that the ultimate product meets the performancespecifications for the part or object. For example, melting point andsoftening point of the polymer may be relevant to both compositeformulation as well as manufacture of the shaped article resulting fromMIM or 3D printing. Additional polymer aspects may include amorphous,crystalline or semi-crystalline character of the base polymer, copolymeror blends.

The waxes useful herein may include paraffin waxes, microcrystallinewaxes, high-density low molecular weight polyethylene waxes, by-productpolyethylene waxes, Fischer-Tropsch waxes, oxidized Fischer-Tropschwaxes and functionalized waxes such as hydroxyl stearamide waxes andfatty amide waxes. It is common in the art to use the terminologysynthetic high melting point waxes to include high-density low molecularweight polyethylene waxes, by-product polyethylene waxes andFischer-Tropsch waxes.

The manufacture of specific articles or shapes by injection molding or3D printing from the particulate is dominated by the physical propertiesof the particulate, such as, for example, size, shape, and morphology,polymer such as, for example, melt flow, and interfacial modifier. Themethods of manufacturing the metal particulate are discussed below inconjunction with the discussion of the particulates themselves. But itis understood that these methods of manufacturing, with suitablemodifications directed to the components and end use of the product, areappropriate for other types of particulate such as inorganic mineralparticulate, glass bubbles and glass spheres, and ceramic particulate.

In an embodiment, a filament or wire is made from the polymer andparticulate coated with interfacial modifier. The coated particulate maybe metal, ceramic, mineral, glass bubbles, glass spheres or combinationsand mixtures. The particulate, interfacial modifier, and polymer stockhas been described supra. Composite material is made by addingparticulate that has been pre-coated or pre-treated with interfacialmodifier to a polymer. Depending on the requirements and specificationsfor making a shaped article via additive manufacturing or injectionmolding techniques, the composition of the filament can be 0.005% to 1,2, 3, 4, 5, 6, 7, 8, 9 or 10 wt. % interfacial modifier, 35% to 40, 55,60, 65, 70, 75, 80, 85, 90, or 95 wt. % of particulate, and 1, 5, 10,15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65 or 70 wt. % of polymer. Thesecomponents are mixed together to make a composite material and thenextruded using an appropriate die to make a filament of a cross sectionthat is suitable to be used in additive manufacturing. Alternatively thecomposite material can be injection molded to provide a shaped article.

The attributes of the composition of the composite material are many.High volume packing, greater than 60%, 65%, 70%, 75%, 80%, 85%, or 90%,are able to be realized with the compositions of the composite material.With said high volume fractions, the mechanical properties of thecomposite material are improved, such as greater impact resistance,increased densification, resistance to oxidation, minimal shrinkage andimproved sintering characteristics for MIM, Press and Sinter, and otherpowder metallurgical processes in comparison to materials that containparticulate this is not coated with an interfacial modifier.

In one embodiment, the initial shapes, such as feedstock, or structuresare made by consolidating the coated metal particulate polymer compositeby heat and/or pressure via extrusion or injection molding. Then, thepolymer is removed by thermal, chemical or other means. In a final step,the metal or particulate mass of the composite becomes very similar tothe characteristics of the pure particulate in a process known assintering. At a minimum, the composite consolidation produces a coherentmass of a definitive size and shape for further processing ordevelopment. The characteristics of the initial pressed shape or objectare influenced by the characteristics of the powder, the grade andmanner of pressure application, the maximum pressure applied, thecreative time of consolidation, the shape of the die, compactiontemperature, and optional additives such as lubricants, alloy agents,dies materials, service conditions and other effects. The compositematerial comprising polymer and interfacially modified particulate at ahigh packing fraction has at least some of the characteristics of theunderlying polymer viscoelastic properties, such as melt flow, elasticplastic deformation, etc., that allows the green body or feedstock to beformed without excessive pressures or equipment wear. After sintering,the object or shape can be worked, heated, polished, painted orotherwise finished into new shapes or structures.

In another embodiment, the feedstock is fed through extrusion-basedadditive manufacturing systems for building 3D models. In brief,“additive manufacturing” or “3D printing” is a manufacturing process formaking a three-dimensional solid object of virtually any shape from adigital model. 3D printing is achieved using an additive process, wheresuccessive layers of material are laid down in different shapes. 3Dprinting is considered distinct from traditional machining techniques,which mostly rely on the removal of material by methods such as cuttingor drilling (subtractive processes). A materials printer usuallyperforms 3D printing processes using digital technology. The 3D printingtechnology is used for both prototyping and distributed manufacturingwith applications in architecture, construction (AEC), industrialdesign, automotive, aerospace, military, engineering, civil engineering,dental and medical industries, biotech (human tissue replacement),fashion, footwear, jewelry, eyewear, education, geographic informationsystems, food, and many other fields. While the skilled man understandsthat we live in a 3D space, in this technology the term 3D refers to aunique manufacturing system as describer above.

Additive manufacturing, or 3D printing, may also be described in severalother computer driven manufacturing processes such as Fused DepositionModeling® (FDM®), PolyJet, Stereolithography (SLA), Selective LaserMelting (SLM), Selective Laser Sintering (SLS), or Direct Metal LaserSintering (DMLS), and Plastic Freeforming. Fused Deposition Modeling®(FDM®) is a technology commonly used for additive manufacturing. Thetechnology was developed in the late 1980s and was commercialized in1990.

Currently, FDM® is often applied in modeling, prototyping, andproduction applications. FDM® uses an “additive” principle. Layers ofmaterial, as a polymer filament or metal wire, is unwound from a coiland supplies material to produce a part. FDM® begins with a softwareprocess which processes an STL file (stereo-lithography file format),mathematically slicing and orienting the model for the build process. Ifrequired by the final product, support structures may be generated.Support structures useful in FDM® can take at least three differentforms or combination of forms. In one example, the support structure canbe in the part itself such as being a component of the legs for a nozzleused for printing. In another example the support structure may befusible or may be sintered with the part formed by FDM®. This type ofsupport may be removable from the part during final processing steps orbecome a component of the part. In a third example, the supportstructure is necessary for the construction of the part via FDM® but thesupport material is removable from the final part. An example of thistype of use for a support material is a venturi made by FDM® The FDM®machine may dispense multiple materials to achieve different goals. Forexample, one machine may use one material to build up the model and useanother material as a soluble support structure, or one could usemultiple colors of the same type of polymer in the same model. The modelor part is produced by extruding small beads of polymer material to formlayers. The layers of material harden immediately after extrusion fromthe nozzle. A plastic filament, metal wire, or composite material of anembodiment is unwound from a coil and supplies material to an extrusionnozzle on the additive manufacturing machine. The machine can turn theflow of the material to the nozzle on and off. There is a drivemechanism, typically some type of worm-drive, that feeds the filamentinto the nozzle at a controlled rate. The nozzle is heated to melt thematerial. For polymers, the polymers are heated past their glasstransition temperature and are then deposited by the extrusion nozzle orprinter head. The nozzle can be moved with high precision in bothhorizontal and vertical directions by a numerically controlledmechanism. The nozzle follows a tool-path controlled by a computer-aidedmanufacturing (CAM) software package, and the part is built from thebottom up, one layer at a time. Stepper motors or servo motors aretypically employed to move and to position the extrusion head. Themechanism used is often an X-Y-Z rectilinear design, although othermechanical designs such as deltabot have been employed. As a printingtechnology FDM® is very flexible, and it is capable of dealing withsmall overhangs by the support from lower layers, FDM® generally hassome restrictions on the slope of the overhang, and cannot produceunsupported stalactites. The myriad choices of materials, such as ABS,PLA, polycarbonate, polyamides, polystyrene, lignin, among many others,with different trade-offs between strength and temperature propertiesare available. In an embodiment the composite material comprisingceramic, glass, mineral or metal particles can be formed into a filamentand delivered by Fused Deposition Modeling® (FDM®).

Another additive manufacturing process is PolyJet printing. PolyJetprinting is a rapid prototyping process where the printers have two ormore jetting heads (one set for the model and one set for the supportmaterial) that spray outlines of the part, layer by layer. The liquidsused are photopolymers, which are cured nearly instantly by a UV lampwithin the printer, creating a solid, plastic-like model that is preciseand accurate. The support material is a gel-like substance, which iseasily washed away. The model has a smooth finish and is ready forsanding, painting, drilling, or tapping. In an embodiment the compositematerial comprising ceramic, glass, mineral or metal particles can beformed into a filament and delivered by PolyJet processes.

Stereolithography (SLA), also known as optical fabrication,photo-solidification, solid free-form fabrication and solid imaging, isone of the oldest types of additive manufacturing or 3D printingtechniques. SLA uses a supply of light-activated polymers as the basematerial and layer by layer of polymer material is then treated with alight source to solidify the polymer layers. Exposure to the lightsource, such as an ultraviolet laser light, cures and solidifies thepattern traced on the resin and joins it to the previous layer. One ofthe advantages of stereolithography is its speed. Functional and usefulparts can be manufactured within a day. The length of time it takes toproduce one particular part depends on its size and complexity and canlast from a few hours to more than a day. Most stereolithographymachines can produce parts with a maximum size of approximately 50×50×60cm (20″×20″×24″) and some, such as the “Mammoth” stereolithographymachine (which has a build platform of 210×70×80 cm), are capable ofproducing single parts of more than 2 m in length. Prototypes or partsmade by stereolithography are strong enough to be machined and can beused as master patterns for injection molding, thermoforming, blowmolding, and various metal casting processes. In an embodiment thecomposite material comprising ceramic, glass, mineral or metal particlescan be formed into a filament and delivered by Stereolithography (SLA).

Selective Laser Melting (SLM) is an additive manufacturing process thatuses 3D CAD data as a digital information source and energy in the formof a high-power laser beam, for example an ytterbium fiber laser tocreate three-dimensional metal parts by fusing fine metallic powderstogether. Most machines operate with a build chamber of 250 mm in X & Yand up to 350 mm Z (although larger machines up to 500 mm X,Y,Z andsmaller machines do exist). The types of materials that can be processedinclude stainless steel, tool steel, cobalt chrome, titanium & aluminum.All must exist in atomized form and exhibit certain flow characteristicsin order to be process capable. In embodiment the IM treated particles,in some embodiments, metallic particles treated with IM, exhibit usefulflow characteristics to the SLM process. Applications most suited to theSLM process are complex geometries & structures with thin walls andhidden voids or channels. Advantage can be gained when producing hybridforms where solid and partially formed or lattice type geometries can beproduced together to create a single object, such as a hip stem oracetabular cup or other orthopedic implant where oseointegration isenhanced by the surface geometry. Much of the pioneering work with SLMtechnologies is on lightweight parts for aerospace where traditionalmanufacturing constraints, such as tooling and physical access tosurfaces for machining, restrict the design of components. SLM allowsparts to be built additively to form near net shape components ratherthan by removing waste material. In an embodiment the composite materialcomprising ceramic, glass, mineral or metal particles can be formed intoa filament and delivered by Selective Laser Melting (SLM).

Selective laser sintering (SLS) is an additive manufacturing techniquethat uses a laser as the power source to sinter powdered material suchas, for example, metal powders, aiming the laser automatically at pointsin space defined by a 3D model, binding the material together to createa solid structure. The process is similar to direct metal lasersintering (DMLS); the two are instantiations of the same concept butdiffer in technical details. SLM uses a comparable concept, but in SLMthe material is fully melted rather than sintered. SLS permits differentproperties such as crystal structure, porosity, and so on to be usefulin the final part. SLS is a relatively new technology that so far hasmainly been used for rapid prototyping and for low-volume production ofcomponent parts. In an embodiment the composite material comprisingceramic, glass, mineral or metal particles can be formed into a filamentand delivered by Fused Selective Laser Sintering (SLS).

Direct metal laser sintering (DMLS) is an additive manufacturingtechnique that uses a laser as the power source to sinter powderedmaterial (typically metal), aiming the laser automatically at points inspace defined by a 3D model, binding the material together to create asolid structure. The DMLS process is similar to SLS. The two areinstantiations of the same concept but differ in technical details. SLMuses a comparable concept, but in SLM the material is fully meltedrather than sintered, allowing different properties (crystal structure,porosity, and so on). The DMLS process involves use of a 3D CAD modelwhereby an stla .STL file is created and sent to the machine's software.A technician works with this 3D model to properly orient the geometryfor part building and adds supports structure as appropriate. Once this“build file” has been completed, it is “sliced” into the layer thicknessthe machine will build in and downloaded to the DMLS machine allowingthe build to begin. The DMLS machine uses a high-powered 200 wattYb-fiber optic laser. Inside the build chamber area, there is a materialdispensing platform and a build platform along with a recoater bladeused to move new powder over the build platform. The technology fusesmetal powder into a solid part by melting it locally using the focusedlaser beam. Parts are built up additively layer by layer, typicallyusing layers 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50 microns(micrometers) thick. This process allows for highly complex geometriesto be created directly from the 3D CAD data, fully automatically, inhours and without any tooling. DMLS is a net-shape process, producingparts with high accuracy and detail resolution, good surface quality andexcellent mechanical properties. Currently available alloys used in theprocess include 17-4 and 15-5 stainless steel, cobalt chromium, Inconel625 and 718, and titanium Ti6Al4V. Theoretically, almost any alloy metalcan be used in this process once fully developed and validated. In anembodiment the composite material comprising ceramic, glass, mineral ormetal particles can be formed into a filament and delivered by DirectMetal Laser Sintering (DMLS).

Plastic Free forming unlike conventional additive manufacturingtechniques, with ARBURG Plastic Freeforming (AKF) standard granulatesare melted as in the injection molding process. The freeformer produceslayer by layer from minuscule droplets. The discharge unit with nozzleremains stationary, while the component carrier moves. The globallyunique AKF process makes use of 3D CAD files, which are read in directlyby the freeformer. After start-up, everything else takes placeautomatically. A nozzle closure with piezo-technology builds up thedesired component layer by layer from minuscule plastic droplets. Duringthis process, the item under construction is moved by a componentcarrier with three or five axes. Fully functional parts are created withminuscule plastic droplets, without a mold. Low-cost standard granulatesare used instead of expensive special materials. No support structuresare necessary as the stationary discharge unit and moving componentcarrier is capable for complex 3D geometries. AKF is also suitable forprocessing two components, e.g. in moving hard/soft combinations. Partsare automatically built up layer by layer on the basis of 3D CAD files.In an embodiment the composite material comprising ceramic, glass,mineral or metal particles can be formed into a filament and deliveredby Plastic Freeforming.

3D printing manufacturing renders virtual blueprints from computer aideddesign (CAD) and “slices” them into digital cross-sections for themachine to successively use as a guideline for printing. Depending onthe machine used, material or a binding material is deposited on thebuild bed or platform until material/binder layering is complete and thefinal 3D model has been “printed.” It is a WYSIWYG (“what you see iswhat you get”) process where the virtual model and the physical modelare almost identical.

To perform a print, the machine reads the design from a computer fileand lays down successive layers of liquid, powder, polymer, paper orsheet material to build the model from a series of cross sections. Inthe embodiments of this application, the viscoelastic compositematerials of the embodiment comprising interfacially coated ceramic,inorganic minerals, metal, or glass bubble particles and spheres areespecially useful in 3D printing manufacture. These layers, whichcorrespond to the virtual cross sections from the CAD model, are joinedor automatically fused to create the final shape. The primary advantageof this technique is its ability to create almost any shape or geometricfeature in three-dimensional space, or xyz-space. 3D printer resolutiondescribes layer thickness and X-Y resolution in dpi (dots per inch), ormicrometers. Typical layer thickness is around 16 to 20, 25, 30, 35, 40,45, 50, 55, 60, 65, 70, 75, 80, 85, 95, or 100 micrometers (μm).Construction of a model with contemporary methods can take anywhere fromseveral hours to several days, depending on the method used and the sizeand complexity of the model. Additive systems can typically reduce thistime to a few hours, although it varies widely depending on the type ofmachine used and the size and number of models being producedsimultaneously.

Such systems are commercially available from Stratasys, Inc. EdenPrairie Minn. After sintering, the object or shape can be worked,heated, polished, painted or otherwise formed into new shapes orstructures.

Metal particulates can be formed into specific structural parts usingconventional technology. Typical materials include iron, iron alloys,steel, steel alloys, brass, bronze, nickel and nickel based alloys,copper, aluminum, aluminum alloys, titanium, titanium alloys, etc. Themetallic particulate can be used to make porous materials such as hightemperature filters, metering devices or orifices, manifolds,reservoirs, brake parts, iron powder cores, refractory materials, metalmatrix composites, and others.

Manufacture

In the manufacture of useful products with the composites of theembodiment, the manufactured composite can be obtained in appropriateamounts, subjected to heat and pressure, typically using powdermetallurgy processes and equipment, such as sintering, and then formedinto an appropriate shape having the correct amount of materials in theappropriate physical configuration.

The manufacture of the particulate and polymer composite materialsdepends on good manufacturing technique. Such techniques are fullydescribed in U.S. Pat. No. 7,491,356 “Extrusion Method Forming AnEnhanced Property Metal Polymer Composite” and U.S. patent applicationpublications U.S. 2010/0280164 “Inorganic Composite”, U.S. 20100280145“Ceramic Composite”, and U.S. 2010/0279100 “Reduced Density Glass BubblePolymer Composite” herein incorporated in their entirety. Often theparticulate is initially treated with an interfacial modifier byspraying the particulate with a 25 wt.-% solution of the interfacialmodifier on the particle with blending and drying carefully to ensureuniform particulate coating of the interfacial modifiers. Interfacialmodifiers may also be added to particles in bulk blending operationsusing high intensity Littleford or Henschel blenders. Alternatively,twin cone mixers can be followed by drying or direct addition to ascrew-compounding device. Interfacial modifiers may also be combinedwith the metal particulate in aprotic solvent such as toluene,tetrahydrofuran, mineral spirits or other such known solvents.

The composite materials having the desired physical properties for MIMand 3D printing can be manufactured as follows. In a Useful mode, thesurface coating of the particulate with the interfacial modifier isinitially prepared. The interfacial modifier is coated on the preparedparticle material, and the resulting product is isolated and thencombined with the continuous polymer phase between the particulate andthe polymer. In the composite, the coating of the interfacial modifieron the particle is less than 1 micron thick, in some cases atomic(0.5-10 Angstroms) or molecular dimensions (1-500 Angstroms) thick. Inone aspect, the function of the interfacial modifier isolates thepolymer from the particle as well as from the other particles. Thepolymer “sees” only the coating material and does not react to theinterfacial modifier coating in any substantial way.

Testing via ASTM D638—10 Standard Test Method for Tensile Properties ofPlastics and ASTM D1238—10 Standard Test Method for Melt Flow Rates ofThermoplastics by Extrusion Plastometer may be performed to characterizethe composite material. Depending on the nature of the final compositematerial, suitable and necessary modifications to the test method may bemade to produce accurate and industrial significant results. Viscositymeasurements for composite materials useful in MIM and 3D Printing aregreater than 30, greater than 40, greater than 50, greater than 60, orgreater than 60 Pa-s.

Once the composite material is prepared, it is then formed into thegreen body desired shape of the end use material for MIM or feedstockfor 3M printing. Solution processing is an alternative that providessolvent recovery during materials processing. The materials can also bedry-blended without solvent. Blending systems such as ribbon blendersobtained from Drais Systems, high density drive blenders available fromLittleford Brothers and Henschel are possible. Further melt blendingusing Banberry, single screw or twin screw compounders is also useful.When the materials are processed as a plastisol or organosol withsolvent, liquid ingredients are generally charged to a processing unitfirst, followed by polymer, particulate and rapid agitation. Once allmaterials are added a vacuum can be applied to remove residual air andsolvent, and mixing is continued until the product is uniform and highin density.

Dry blending is generally useful due to advantages in cost. Howevercertain embodiments can be compositionally unstable due to differencesin particle size. In dry blending processes, the composite can be madeby first introducing the polymer, combining the polymer stabilizers, ifnecessary, at a temperature from about ambient to about 60° C. with thepolymer, blending a particulate (modified if necessary) with thestabilized polymer, blending other process aids, interfacial modifier,colorants, indicators or lubricants followed by mixing in hot mix,transfer to storage, packaging or end use manufacture.

Interfacially modified materials can be made with solvent techniquesthat use an effective amount of solvent to initiate formation of acomposite. When interfacially modification or interfacial treatment issubstantially complete, the solvent can be stripped. Such solventprocesses are conducted as follows:

-   -   1) Solvating the interfacial modifier or polymer or both;    -   2) Mixing the metal particulate into a bulk phase or polymer        master batch: and    -   3) Devolatilizing the composition in the presence of heat vacuum        above the Tg of the polymer

When compounding with twin screw compounders or extruders, a Usefulprocess can be used involving twin screw compounding as follows.

1. Add metal particulate and raise temperature to remove surface water(barrel 1).

2. Add interfacial modifier to twin screw when the particulate is attemperature (barrel 3).

3. Disperse/distribute/coat interfacial modifier on particulate.

4. Maintain temperature to completion.

5. Vent VOC (barrel 6).

6. Add polymer binder (barrel 7).

7. Compress/melt polymer binder.

8. Disperse/distribute polymer binder in particulate.

9. Blend modified particulate with polymer melt binder.

10. Vacuum degas remaining VOC (barrel 9).

11. Compress resulting composite.

12. Form desired shape, green body, feedstock, pellet, lineal, tube,injection mold article, etc. through a die or post-manufacturing step.

13. Debinding

14. Sinter

Alternatively in formulations containing small volumes of continuousphase:

1. Add polymer binder.

2. Add interfacial modifier to twin screw when polymer binder is attemperature.

3. Disperse/distribute interfacial modifier in polymer binder.

4. Add filler and disperse/distribute particulate.

5 Raise material to temperature.

6. Maintain temperature to completion.

7. Compress resulting composite.

8. Form desired shape, green body, feedstock, pellet, lineal, tube,injection mold article, etc. through a die or post-manufacturing step.

9. Debinding forming the brown body or part.

10. Sinter

The composite formulation for shaped article of a green body orfeedstock, whether formed with interfacially modified ceramic, metal,inorganic, or glass bubble particulate, has attributes of a high volumeparticle fraction packing, and improved mechanical/physical propertiessuch as viscoelasticity and melt flow. After sintering the shapedarticle can have increased densification, resistance to oxidation, andminimal shrinkage. The post-sintered shaped article has the physicalcharacteristics of the underlying particulate. Further, the sinteringprocess is much improved due to the characteristics and properties ofthe viscoelastic composite.

For powder injection molding, metal injection molding or additivemanufacturing with the disclosed composite material, the particulatematerial such as ceramic, inorganic, glass, metal particulate arenon-ductile resources but they can be used in shaping processes, if theyare mixed with materials such as organic substances. These organicsubstances are, such as for example polymers, also called “binder”.

The use of polymer as a binder varies according to the processing methodand the particulate mixture. Binders give the green body a sufficientstrength by associating particles at their boundary surfaces. Usuallythose binders are used as plastification agents. They make possible theflow of the particulate during processes such as extruding, injectionmolding, and additive manufacturing. The interfacially modifiedparticulate can attain volume or weight packing levels in the compositematerial that are greater than theoretical, but the composite materialdoes retain its melt flow and rheological characteristics that areuseful in extrusion, metal injection molding and additive manufacturing.

In brief, the process for powder injection molding, metal injectionmolding or additive manufacturing with the disclosed composite materialmay take many variations, but the key steps are 1) feedstock preparationof the composite material used for the body of a part or object, 2)injection molding or laying down of layers of composite material usingadditive manufacturing techniques to form a “green body” of the part orobject, 3) debinding the part or object, and 4) sintering the part orobject. Preparation of the feedstock or the composite material of theembodiment to provide a homogeneous, highly packed coated particulate,injection molding and additive manufacturing processes have beendisclosed.

Before sintering green bodies, the debinding process of the polymers toform the brown body, such as, for example, the removal of the polymermaterial, must be performed. The removal of the binder is viadegradation, extraction or evaporation via the surface channels in the“green body”. Debinding can be the most time consuming and expensivestep in the part or object formation. Debinding the part may be done viathermal, solvent or catalytic methods. Binder material is chosen basedon the selection of the debinding method. The composite material of theembodiment, comprising particulate that is coated with interfacialmodifier, improves the debinding process by allowing debinding toproceed more quickly and efficiently than particulate that is uncoated.The higher volume or weight fractions of the coated particulate permitsthe use of less binder in the part or object, and the rheology and meltflow of the composite material provide for the part or object to be morequickly formed. Such higher particulate fractions are not possible withuncoated particulate.

The temperatures for thermal debinding vary between 60° C. and 600° C.Organic polymers have to be removed completely from the green body,since carbon delays and can influence the sinter process. Further thequalities of the final product can be negatively impacted by residualcarbon from the polymer. The debinding process typically is a timeintensive step in the complete production process. The speed ofdecomposition of the polymers should not exceed the transport velocityof the products of pyrolysis, since an excess pressure of the gaseouspyrolysis products can lead to rips and to the destruction of the brownbody.

During raw material preparation the binder has to give an optimumbinding to the green body. A minimum of binder quantity should realizethe desired plasticity of the compound and to avoid forming byproductsduring debinding that could negatively affect the final part or object.Requisites for an effective binder can be defined as follows: 1) Thestructure of the binder must allow a preparation of the compound withlow abrasion to the equipment be it extrusion, injection molding oradditive manufacturing. 2) The binder should be processable withoutdecomposition in a temperature range of 20° C. to 350° C. relative tothe rate of the melt processing or additive manufacturing procedure. 3)In order to protect the operating personnel toxic substances should beavoided. 4) The melting point of thermoplastic binders should be as wideranging as is demanded by the forming machine be it injection molding oradditive manufacturing. 5) Stabilization against deterioration ofmicroorganisms is necessary and of oxidation or light ageing inthermoplastic systems. 6) The binder should grant a sufficient stabilityof the formed product for non-destructive transport or for mechanicalfinishing.

Binders can be classified into three classes 1) slip additives, 2)binding agents and 3) plasticizers or plastification agents. Slipadditives are used to reduce the internal friction of particulatesduring pressing and to allow a non-destructive and fast release of themold from the die. Slip additives are added as aqueous solutions incorresponding concentrations or as powder, which will be mixed with themass. Binding agents are added to increase the flexural strength of thepressed body and plastification agents may increase the plasticity ofthe mass especially when the forming will be done in piston presses orin screw extrusion presses. The amount of plastification agents variesbetween 0.2% and 1% and depends on the grain size of the mass, on thedimension of the mold and the pressure of the press.

Organic plastification systems have to be distinguished between 1)aqueous systems, 2) solvent containing systems, and 3) thermoplasticsystems. Aqueous plastification systems consist of dispersions orsolvents of polymers where the water has the function of deflocculant orsolvent. The effectivity of plastification is not only caused by thestructure of polymers but also supported by the water content. Solventcontaining systems are disappearing in particulate production facilitiesbecause of the increasing demands of environment protection, workplacehygiene and safe working conditions. Thermoplastic systems wereoriginally developed for injection molding machines in the plasticsindustry. Thermoplastic systems are exemplified, for example, byparaffin, wax, polyolefin wax materials; thermoplastic resins such aspolyolefin, polypropylene (PP), polyethylene (PE), polyacetal,polyoxymethylene (POM). Molecular chains of polyolefin thermoplastic,polypropylene (PP) and polyethylene (PE) resins are much longer thanthose of waxes. This difference arises in higher binding forces ofthermoplastics and as a consequence a higher melting viscosity andmelting point.

The thermal treatment of the debinding process destroys the polymers byoxidation or combustion in an oxygen containing atmosphere. Very oftenit is an uncontrolled reaction of high reaction rate inside the shapedpart creating a high gas pressure, which can lead to ruptures within thepart. It is useful to transfer reactive thermoplastics into amodification of radical decomposition, which is easier to oxidize. Thisis a way to transfer polymers of high viscosity into substances of oilyconsistency. The radical decomposition will start with a definedtemperature and continue as a chain reaction. Also in hydrogenatmospheres a de-waxing process can be accomplished, but of courseinstead of an oxidation a hydrogenation of decomposition products willoccur.

The defining physical procedures of thermal debinding are 1) thecapillary flow, 2) the low pressure diffusion process, and 3) the highpressure permeation process. The capillary forces involve liquidextraction, while the other two require the binder to be a vapor.Slightly elevated temperatures influence the viscosity and surfacetension of the organic liquid; capillary forces start with the transportof the liquid phase from big to small pores. As soon as binder arrivesat the surface it will be vaporized, if its vapor pressure is largerthan the ambient pressure. With increasing temperature, the kinetics ofvolatilisation increases too. Above a certain temperature the capillaryforces cannot saturate the demand of volatilisation of the liquid at thesurface and the interface of both the vapor and the liquid is pulledback to the inside of the body. The binder may be thermally decomposedinto low molecular weight species, such as H₂O, CH₄, CO₂, CO etc. andsubsequently removed by diffusion and permeation. The difference betweendiffusion and permeation depends on the mean free path of the gasspecies. The mean free path varies with the pressure, molecular weightof the gas and pore dimensions. Generally, diffusion will be dominant atlow pressures and small pore sizes; permeation would be expected tocontrol debinding with large pore sizes and high vapor pressures, wherelaminar flow controls the rate of gas exit from the compact. Typicallythe pressure of a debinding process varies between 10⁻³ bar and 70 barand the grain sizes between 0.5 and 20 mm.

The thermal decomposition of polymers takes place by radical splittingof their chain. A homolytic decomposition of a C—C-bond leads to radicalcracked products. Homolytic means the symmetric decomposition of theduplet. The intermolecular transfer of hydrogen and the continuousdecomposition of the polymeric chain create saturated and unsaturatedfractions consisting of monomers and oligomers during the debindingprocess.

“Sintering is the process whereby particles bond together typicallybelow the melting point by atomic transport events. A characteristicfeature of sintering is that the rate is very sensitive to temperature.The driving force for sintering is a reduction in the system freeenergy, manifested by decreased surface curvatures, and an eliminationof surface area” (Powder Metallurgy Science, 1989, pg. 148). Theinterfacial modifier on a particle surface may cooperate in thesintering process to the level of fusing with other interfacial modifiercoatings on other particles to form the sintered product. Theinterfacial modified surfaces that fuse or sinter may be the same ordifferent relative to the organo-metallic interfacial modifier. Further,the grain boundary, the interface between particles, may fuse or sinteras well.

The steps in sintering for MIM or 3D Printing may be summarized asfollows:

-   -   1) Feedstock or composite compounding.    -   2) 3D printing or injection molding of feedstock or composite to        form a green body or a preform.    -   3) Debinding, thermally, chemically or other means, of the green        body to form the brown body.    -   4) Sintering the brown body to form the sintered part.    -   5) Post sintering finishing.        If required for product specifications, inert, reducing and/or        oxidizing atmospheres, applied during the appropriate stage of        the sintering process, may provide useful characteristics to the        final product. The gases that can be used to provide these        atmospheres are argon, nitrogen (inert), hydrogen (reducing),        and oxygen, air (oxidizing). If appropriate, the sintering step        may occur under vacuum.

Example 1

The metal particles were Carpenters 316L stainless steel (90%<16 μm) anda special cut of Ervin ES-140 stainless steel (+150 to −106 μm). Theparticles were blended in a 3:1 (bigs:smalls) ratio. The raw particleswere added to a lab scale mixer for about 5 minutes to obtain an evenlydistributed blend. Isopropyl alcohol was added into the mix. Titaniumtri isostearoyl isopropoxide, CAS RN 61417-49-0, was then added at adosage level of 1.0 pph. The batch was mixed and heated to about 90° C.,until all IPA evaporated off the treated powder. Current BatchFormulation: 2100 g ES-140, 700 g 316L, and 28 g Titanium triisostearoyl isopropoxide. Treated particles were compounded with TPX®DX310 (Poly methyl-pentene, Mitsui Chemicals) at 75% of treatedparticles.

The maximum loading ratio of treated particles to polymer was calculatedbased upon pyncnometer density and powder puck density, shown inEquation 1. This value was the theoretical maximum attainable volumefraction of treated particles in the product.

$\begin{matrix}{{{Maximum}\mspace{14mu}{Loading}} = \frac{{Powder}\mspace{14mu}{Press}\mspace{14mu}{Density}}{{Pycnometer}\mspace{14mu}{Density}}} & (1)\end{matrix}$

A treated volume fraction was chosen based upon the calculated maximumloading; this volume fraction was generally lower than the calculatedvalue. The treated particles were compounded on the 19 mm lab scalecompounder with the polymer TPX® DX310 (Poly methyl-pentene, MitsuiChemicals), a polyolefin polymer.

As an initial test, a powder disk with treated particles was pressed ina mold. A powder puck was formed by pressing the treated powders 30times to maximum pressure on the lab jacks. The dimensions of the puckwere measured in order to provide a comparative analysis between thesample before and after the sintering process.

Two pucks, each about 3.5 mm thick, were then made using materialcompounded with the TPX® DX310. Densities of each were calculated, andthe pucks were placed one on top of the other. Here, the purpose was tosinter the two pieces together and calculate a new density of thesintered piece.

Upon completion of compounding, pellets were extruded on the wire line.The wire line has a 1″ extruder and a 0.075″ diameter die. The extrudercontains 3 zone temperature controls within the barrel, as well as a dietemperature control. The back two zone temperatures are kept well belowthe melting point of the polymer, which acts as a reduction of thebarrel length and thus reduces the resonance time of the material attemperature. Extruded material was drawn down to a diameter of about0.068-0.072″ and spooled up. The viscosity of this material was 43.1Pa*s.

Strips of wire were then stacked upon one another to simulate a 3Dprinted part for sintering.

The sintering process occurred in a tube furnace. This furnace waspurged with Nitrogen/Hydrogen gas in order to prevent any oxidation ofthe sample. The material is heated under vacuum to 1250° C., at a rateof 300° C. per hour. The furnace was then held at temperature for anhour before being cooled back to room temperature.

In the appropriate product design, during composite manufacture orduring product manufacture, a pigment or other dye material can be addedto the processing equipment. One advantage of this material is that aninorganic dye or pigment can be co-processed resulting in a materialthat needs no exterior painting or coating to obtain an attractive,functional, or decorative appearance. The pigments can be uniformlydistributed throughout the material and can result in a surface thatcannot chip, scar or lose its decorative appearance. One particularlyimportant pigment material comprises titanium dioxide (TiO₂). Thismaterial is extremely non-toxic, is a bright white particulate that canbe easily combined with either metal, glass, non-metal, inorganic ormineral particulates to enhance the novel characteristics of thecomposite material and to provide a white hue to the ultimate compositematerial.

We have further found that a blend of two, three or more metal, glass,non-metal, inorganic or minerals in particulate form can obtainimportant composite properties from all of metal, glass, non-metal,inorganic or minerals in a composite structure. Such composites each canhave unique or special properties. These composite processes andmaterials have the unique capacity and property that the material actsas a blended composite of two or three different glass, metal,non-metal, inorganic or minerals that could not, due to melting pointand other processing difficulties, be made into a blend without themethods of the embodiment.

Example 2 Zirconium Silicate

We obtained the zirconium silicate (ZS) spheres in the 70-125 micronsize range (product name ZS B0.07) from Stanford Materials (CA). Theuncoated helium pyncnometer density of the zirconium silicate wasdetermined to be 3.78 g/cc. Packing density using the metallurgicalpress was determined to be 2.42 g/cc yielding a packing fraction of64.1% for the unmodified and 2.53 g/cc and 69.2% for particulatesmodified with 2 phr NZ-12 (the pyncnometer result for the modifiedzirconium silicate was 3.657 g/cc). The results indicate that theinterfacial modifier increases the ability to increase packing of thezirconium silicate spheres.

Unmodified ZS-B0.07 was compounded with THV 220A using the 19 mm B&Plaboratory compounder at a target loading of 60 volume %. The compounderwas equipped with a 3 hole die and was using the 4 blade pellet cutterat 100 RPM. At a set compounder screw speed of 185 RPM with a flat 185°C. temperature profile, the compounder exhibited torque of 30-35% ofmax, pressure of 80-110 psi and a melt temperature of 200° C. A puck ofthe compounded pellets had a density of 3.03 g/cc which was within 2% ofthe target density.

Interfacially modified ZS was also compounded with THV 220A also at atarget loading of 60 volume % zirconium silicate. To maintain a 60.1 vol% particles (treating the ZS as the particle and the coating layer andthe THV as the continuous matrix phase in the composite) a mass ratio of23.2 wt % THV and 76.8 wt % coated ZS was used. A metallurgical press ofthe compounded pellets produced a puck with a density of 2.965 g/ccwhich was within 2% of the target density.

Both materials were extruded at temperature profile of 154, 150, 150,140° C. from throat to die but motor load was not recorded for eitherrun due to attention on feed and extrudate using a 19 mm 3 mmrectangular shaped die plate. The finish was good for both materials, nonoticeable difference, but the flexibility of the materials was obviouswhen a section was bent. The modified material was flexible whereas theunmodified material was brittle.

Tensile samples were cut then pulled at one inch per minute using thetensile tester. FIG. 3 shows the average tensile response of the coatedand uncoated materials compared to pure THV 220A. Stress/strain curveswere determined using type-IV dogbones with brittle (uncoated) andelastic (when coated at 2 phr of NZ-12) behavior observed.

Because the physical properties (tensile stress/stain curves) andprocessing within compounding and extrusion were favorable when loadingTHV220 to about 60 volume % zirconium silicate, we proceeded with aprocess study to confirm the metallurgical press results that reveal theability to pack the coated zirconium silicate to a higher level than theuncoated material.

2^(nd) Experiment: Determining Maximum Packing Level with the 19 mmCompounder:

Throughout the experiments, the volumetric throughput was kept constantat 60 cc/min with an isothermal temperature profile of 185° C. and ascrew speed of 185 RPM and a three hole pellet die plate. Tables 4 and 5show data for composites with unmodified and modified particle.

TABLE 4 Uncoated Vol. % Z. Silicate Torque (%) Pressure (psi) Melt T (°C.)  0 (all THV) 25 0 195 60 40-45 210 204 64 50 430 208 68 65 750-810224 70 65 900 235 72 Overload — — 70 (replicate)* 75-80 1070 242 71* 951270 250 *Note, gathered strands and determined puck density of 3.05g/cc vs a 3.26 composite density that would correlate to 70%. This valueindicates that the composite is starved of polymer resulting in voidswithin the composite.

TABLE 5 Coated with 2% NZ-12 Vol. % Zr Silicate Torque (%) Pressure(psi) Melt T (° C.) 70 40 400 +− 50 211 72 60 400 +− 50 230 74 60 300229 77 50 220 222

Note the reduced torque and pressures associated with the modifiedmaterial run at a given volumetric level (e.g. 70 volume %). Processingat a higher packing indicated a lower particle:particle friction levelin the modified particles; a puck density of the combined levels (70-77volume %) was 2.96 g/cc. The results indicate that the composite sampleswere polymer starved at particulate levels beyond the packing fraction(a trend that explains the lower torque and pressures as zirconiumsilicate levels increased).

This inorganic or ceramic composite material is formed into a filamentby extrusion processes and the filament is used in FDM® to provide apart or object.

In summary, the composites, as dictated by the specific claims containedherein, represents a breadth of raw material combinations including;metals, inorganic particles, ceramic particles, glass bubble particles,polymers, interfacial modifiers, other additives, all with varyingparticle sizes, weight fractions, and volume fractions. The presentembodiment also includes a breadth of processing methods, such assintering and densification, resulting physical and chemical properties,and end-use applications. The following materials exemplify theembodiments of the disclosure. The composite materials can all be formedinto a filament, printed via additive manufacturing techniques, molded,extruded, and sintered to make into useful composites, shapes, andarticles.

I claim:
 1. A filament adapted for use in an additive manufacturingsystem, the system comprising a digitally controlled applicator that candeposit the filament in a controlled x-y plane and in a z-directionfilament application to obtain a pre-form object; the filamentcomprising: (a) about 15 to 1 wt. % of a thermoplastic polymer; and (b)about 99 to 85 wt. % of a ferrous metal particulate, dispersed in thepolymer, the particulate having a particle size of less than 500microns, and an exterior coating of interfacial modifier on theparticulate in an amount of about 0.005 to 2 wt. %, all percentagesbased on the weight of the filament.
 2. The filament of claim 1 whereinthe metal particulate comprises a blend of a first particle and a secondparticle with a size ratio of between about 2:1 to 7:1.
 3. The filamentof claim 1 wherein the first particle as a particle size of 4 to 100μand the second particle as a particle of 5 to 50μ.
 4. The filament claim1 wherein the filament comprises a stainless steel particulate.
 5. Thefilament of claim 4 wherein the filament comprises the stainless steelparticulate dispersed in a polyolefin.
 6. The filament of claim 1wherein the filament comprises a generally circular cross-section with adiameter of about 0.1 to 5 millimeters.
 7. The filament claim 1 whereinthe interfacial modifier comprises an organometallic compound selectedfrom the group of organo-titanium compound, organo-zirconium compound ormixtures thereof.
 8. A thermoplastic pellet adapted for use in aninjection molding manufacturing system, the system comprising anextruder and a heated die, to obtain a pre-form object; the pelletcomprising: (a) about 15 to 1 wt. % of a thermoplastic polymer; and (b)about 99 to 85 wt. % of a ferrous metal particulate, dispersed in thepolymer, the particulate having a particle size of less than 500microns, and an exterior coating on the particulate of an interfacialmodifier in an amount of about 0.005 to 2 wt. %, all percentages basedon the weight of the pellet.
 9. The pellet of claim 8 wherein the metalparticulate comprises a blend of a first particle and a second particlewith a size ratio of between about 2:1 to 7:1.
 10. The pellet of claim 9wherein the first particle as a particle size of 4 to 100μ and thesecond particle as a particle of 5 to 50μ.
 11. The pellet of claim 8wherein the pellet comprises a stainless steel particulate.
 12. Thepellet of claim 8 wherein the pellet comprises a generally circularcross-section with a diameter of about 0.1 to 5 millimeters.
 13. Thepellet claim 8 wherein the interfacial modifier comprises anorganometallic compound selected from the group of organo-titaniumcompound, organo-zirconium compound or mixtures thereof.
 14. A method ofmaking an object with an additive manufacturing system, the methodcomprises: (i) depositing a filament, with the system comprising adigitally controlled applicator, in a controlled x-y plane withsubsequent z-direction filament application to obtain a preform object;the filament comprising: (a) about 15 to 1 wt. % of a thermoplasticpolymer; and (b about 99 to 85 wt. % of a ferrous metal particulate,dispersed in the polymer, the particulate having a particle size of lessthan 500 microns, and an exterior coating on the particulate of aninterfacial modifier in an amount of about 0.005 to 2 wt. %, allpercentages based on the weight of the filament; and (ii) sintering thepreform object to remove the polymer and bond the particulate formingthe object.
 15. The method of claim 14 wherein the preform ismechanically shaped prior to sintering.
 16. The method of claim 14wherein the filament is deposited at a rate of about 15 to 200 mm-sec⁻¹.17. The method of claim 14 wherein the preform object is sintered at atemperature greater than about 1000° C.
 18. The method of claim 17wherein in sintering the preform object, the preform object is sinteredby increasing the temperature at a rate greater than 100° C. per hourbeginning at an initial temperature.
 19. The method of claim 14 whereinthe preform object comprises a first filament and a second filament thesecond element comprising either a particulate or a polymer differentthan the first filament.
 20. The method of claim 14 wherein thesintering is conducted in a nonoxidizing atmosphere.